My Fire baby girl supposedly had 3 live meals [questionable] and when I offered her a thawed hopper, she sniffed it a bit, picked it up, dragged it into her little half-coconut shell hide and ate it.
I suspect that possibly, hungry hatchlings might be able to be started on F/T.
If I ever get any hatchlings, I'm gonna give it a shot.
I just picked up a 5 year old adult who'd never had F/T in his life and he immediately ate.
I have two others [male Fire, male Bee] who simply, utterly refuse to switch, no matter what.
My het Clown girls will go off feed and one live feeding kicks them back into gear for F/T.
I have no idea why.